Laser Pegs are a toy consisting of clear plastic blocks containing LEDs and wiring, with the convenient trait that the blocks happen to be roughly physically compatible with Lego parts. They don’t exactly say “Lego”, but they indicate compatibility with “other construction kits”. They mean Legos.

Quick summary of things you might want to know:

1. The blocks themselves are of tolerable quality. They are not as good as Lego parts. I’ve found bits of flash left over from the molds on several pieces, which is harmless, and a few of them haven’t been quite as solid a fit as I’d expect from new Lego parts. I have 25-year-old lego pieces that stay stuck together more reliably than a few of these pieces. Most of them are fine, but the quality control might be a bit erratic.
2. The packaging is not particularly good. One of the things I loved about the larger lego sets I got as a kid is that the large box would contain some kind of arrangement of trays and pieces such that I could continue using it to hold and sort pieces later. Not so much with these; in general, it’s plastic bags taped to large hunks of cardboard. This is pretty minor, but it might matter if you’re wondering whether you want some kind of alternative storage device.
3. The AC adapter is 5V, the three AA batteries are of course 4.5V. The actual voltage on the connectors, though, seems to be 3.3V. This might matter if you wanted to use these with hardware that had 3.3V outputs, like the GPIO pins on a Raspberry Pi. More testing reveals a broader range of voltages; I’ve measured the outputs on that gizmo at anywhere from 3.3V to 4.3V or so. I’m guessing the LEDs are pretty tolerant, but they do seem to come on as low as 3.3V.
4. There are dire warnings not to, say, plug the AC adapter into the pins coming out of the power supply base thing. There are no warnings at all about how to connect the pieces, except that you shouldn’t connect more than 200 of them. This leads me to suspect that they’ve done a decent job of configuring things with diodes, etcetera, to avoid electrical problems.
5. Which is not to say you might not get some surprises. In particular, power only flows one way. Without loss of generality, call the holes in the power supply base “female” and the connectors that plug into those “male”. Most pieces have at least one male and one female connector. Power can flow from a female connector to a male connector, but not the other way around. So when planning construction, remember that it’s not enough that everything be connected; they have to be connected such that there is a power flow to them.
6. Nearly all pieces have at least one LED, although some small corner adapters don’t. Some have two. Of the 4×4 grid pieces I have, at least a couple have two LEDs, and at least a couple have only one.
7. LEDs are white, blue, green, yellow, orange, and red. I have not seen any purple. There is usually a tiny mark somewhere on the (white plastic) circuit board indicating the color of the LEDs. No part I’ve found has two different colored LEDs in it. The white is the standard “white LED” which is called “cool white” in christmas light sets.
8. I have no information about actual power consumption per se, but I note that the AC adapter is rated for 2000mA, and they ask you not to connect more than 200 of the colored lighting bits. I don’t know how efficient the conversion from 5V to 3.3V is, or how much margin they’re leaving, but you can probably do okay with a ballpark assumption that the LEDs are not using much over ~.05W (assuming about 10mA of the 5V supply’s capacity per thing plugged in), which would suggest that you budget for about 15mA at 3.3V. Maybe. A bit of messing around with an ammeter got an estimate of 110mA of current draw for 18 of the LEDs at around 4.3V, which is more like 7mA each. Your mileage, it appears, may vary.
9. The 2×4 bricks are 1 2/3 standard brick heights tall. The 4×4 are unusual in that they have dots on both sides. This may impact your planning if you want to combine these with other kits.

Hope this is of use to people. My conclusion: Nicely done toy, lots of potential. I would be happier if they had purple LEDs, made it easier to pick and choose by color, and had slightly better quality control on the generic plastic building parts, but they’re not bad or anything.